Polyurethane sealant containing trialkyloxysilane end groups

ABSTRACT

A polyurethane sealant composition containing terminal-NCO groups, at least 5 percent of the -NCO groups being end-blocked with -Si(OR)3 groups, where R is a lower alkyl. The terminal silane groups provide adhesion retention of the sealant to substrates such as metal or glass even after prolonged water immersion.

United States Patent [72] inventor George M. Seiter Continuation-impartof application Ser. No. 746,305, now abandoned. This application May 28,1970, Ser. No. 41,597

[54] POLYURETHANE SEALANT CONTAINING TRIALKYLOXYSILANE END GROUPS 17Claims, No Drawings [52] U.S.Cl 260/37 N,

117/124 E, 260/75 NE, 260/775 A, 260/775 AM, 260/775 MA, 260/77.5 AP

[51 Int. Cl C08g 22/08 [50] Field of Search 260/77.5 A, 77.5 AP, 77.5AM, 75 NA, 37 N I 56] References Cited UNITED STATES PATENTS 3,246,6714/1966 Stein et al. 138/109 3,309,261 3/1967 Schiller et a1. 161/190Primary Examiner- Donald Ev Czaja Assistant ExaminerM. J. WelshAltorneyKinney, Alexander, Sell, Steldt & Delahunt tendon 01 th: sealantto substrates such as metal or glass even after prolonged waterimmersion.

POLYURETHANE SEALANT CONTAmllNG TMALKYLOXYSHLANE END GROUPS Thisapplication is a continuation-in-part of my copending application Ser.No. 746,305, filed July 22, 1968, and now abandoned which in turn is acontinuation-in-part of Ser. No. 480,138, filed Aug. 16, 1965 and nowabandoned.

This invention relates to improved polyurethane materials useful asadhesives, coatings and sealants which provide moisture-resistant bonds.More specifically it relates to such materials which have exceptionaladherence to siliceous and metallic substrates.

It has been proposed to use various silicones or silanes as primers foradhesives applied to substrates such as glass; see for example, Mulleret al. US. Pat. No. 3,032,439, issued May 1, 1962. Such compositionshave also been used as integral blend additives for sealants. Knownpolyurethane sealant compositions, even when primed, fail adhesivelyafter relatively short periods of water immersion.

The present invention has provided an adhesive or sealant which rapidlyachieves high-bond strength to unprimed substrates and which forms bondshaving exceptional durability after prolonged water immersion. Theseresults are obtained by providing an elastomeric polyurethane sealantmaterial having silane groups thereon. These silane groups are presentat the ends of the polyurethane polymer chains. It is theorized that theSi(OCl-l groups at the ends of the polymer chains hydrolyze on thesurface to which the sealant is applied to form --Si(Oll-l) and thatpossibly a condensation takes place, e.g. with SiOH in a siliceoussubstrate or with a metal oxide in a metal substrate to form a permanentchemical bond. Although the exact adhesive mechanism is unknown, thebonds to nonporous substrates produced by the sealants of the presentinvention provide hitherto unobtainable permanency.

The sealants of the present invention have exceptional utility in suchapplications as automotive windshield sealants, bath tub caulkings,window glazing, and potentially as a general construction sealant. Thesealants are curable at room temperature and in the absence of additivesare normally honeylike liquids. It is preferred for many sealing orcaulking applications to fill these liquids with an ingredient such astale to form thixotrope for caulk gun or spatula application. Thesealants cure to form a tough, rubbery product either by interactionwith moisture in the atmosphere or reaction with other curing agentscontaining two or more active hydrogen atoms.

In formulating adhesives, additives such as tackifying resins andstabilizers are included depending on the use for which the adhesive isintended. Crosslinking agents can be incorporated and by varying theamounts of the same, the properties of the final cured product can bevaried from a soft rubber to relatively hard rubbers.

The preferred embodiments of the invention involve the formation of apolyurethane prepolymer by reacting a diisocyanate with compounds havingtwo or more active hydrogens. By active hydrogens," as the term is usedherein, is meant hydrogens which display activity according to theZerwitinoff test described in J.A.C.S. 49, 3l8l (i927). Typical groupscontaining reactive hydrogen are hydroxyl, carboxyl, primary amino andsecondary amino groups.

An excess of isocyanate should be present so that the prepolymer is anNCO terminated material. The ratio of NCO groups to active hydrogens ispreferably between about 1.421 to about 3:1 for moisture curing,one-part sealants. The NCOl-OH ratio can be as low as about 1.05:1 fordiisocyanate/diol prepolymers and can be as high as 6 in the case oftwo-part sealants in which an isocyanate adduct forms one part and acoreactant such as a polyol or a polyamine forms the other coreactant.It has been found that the NCO terminated prepolymer can be capped orend-blocked with a silane if the silane added contains a single-activehydrogen atom, so that the silanes will not be chemically taken up intothe middle of the polymer chains.

Silanes useful in the practice of the invention are those of the generalformula where R is a lower alkyl group, preferably CH R1 is O., S, or Naryl, or

hydrogens, aryl,v substituted alkyl, substituted lhfigroup where R, isan alkyl, aryl, substituted alkyl or substituted v aryl group.

R, R R,, R, and R, are free of active hydrogens and H is an Q activehydrogen. v Examples of compounds falling within this generalizedformula include alkylaminoalkyltrialkoxysilanes, such as CHNH(CH2)3Sl(OCHa)3 or v s( 2)a 2)a a)s, captoalkyltrialkoxysilanes, suchas HS(CH2) Si(OC H hydroxyalkyltrialkoxysilanes.

Other examples will be readily apparent to those skilled in the art.

A significant percentage of the NCO groups of the prepolymer should beend blocked with -Si(OCH,), radicals in order to provide strong bondswith siliceous substrates. Preferably enough silane is added to reactwith about l0 percent of the NCO groups. Useful results can be achievedby using enough silane to react with between about 5 and 50 percent ofthe NCO groups. Less than about 5 percent does not provide significantimprovement in adhesive qualities, while more than about 50 percentresults in a soft polymer having less cohesive strength. End blocking ofup to percent of the NCO groups does, however, provide polymers withsuffcient cohesive strength for a variety of applications. The preferredratio is from about 10 percent to 20 percent of equivalents of silane toisocyanate groups, superior results being obtainable in this range. Inthe embodiments of this invention wherein enough silane is used to reactwith (Le. provide end-capping of) more than 50 percent of the NCOgroups, it is particularly desirable to end-cap polyurethane prepolymersformed from arylene diisocyanates and polyoxyalkylene polyols. In atypical formulation of this type, a sealant which is about 100 percentend-blocked is made from 6 moles of polyoxypropylene glycol, 7 moles oftoluene diisocyanate, and about 2 moles of a suitable secondaryaminosilane. Formulations of this type can also include polyoxypropylenetriols and the like.

The preferred active hydrogen containing materials for use in formingthe sealants of the present invention are polyalkylene ether glycols.Such glycols may also contain triols to provide a crosslinked product.Other reactants containing active hydrogens such as diamine, -Sl-lterminated polyethers, and hydroxyl terminated polyesters, can be usedin place of or in combination with polyether diols. Active hydrogencontaining polymeric materials which are preferred for making rubberysealants and which result in products having a good balance ofelasticity and cohesive strength are those which have an averagemolecular weight between about 400 and about 6,000. More rigidstructural adhesives can be formed using lower molecular weightmaterials.

Various organic diisocyanates may be used in the practice of theinvention. Because of their ready availability and the fact that theyare liquid at room temperature, mixtures of the 2,4- and 2,6-toluenediisocyanate isomers are preferred in the practice of the invention.Other useful aromatic diisocyanates include paraphenylene diisocyanate,meta-phenylene diisocyanate, 4,4-diphenyl diisocyanate, 1,5 naphthalenediisocyanate, 4,4-diphenyl methane diisocyanate, 4,4'-diphenyl etherdiisocyanate, 3,3 dimethyl 4,4 diphenyl diisocyanate and 3,3 dimethoxy4,4 diphenyl diisocyanate. Suitable aliphatic diisocyanates include thesimple alkyl diisocyanates such as hexamethylene diisocyanate as well asmore complex materials such as bis( 2-isocyanatoethyl) fumarate,bis(2-isocyanatoethyl) carbonate, bis(2-isocyanatoethyl)-4-cyclohexenel.2-dicarboxylate, bis( 2-isocyanatoethyl) l ,4,5,6,7,7'hexachloro-S-norbomene-Z,3-dicarboxylate.

in order to cause the polyurethane reaction mixtures of the presentinvention to form elastomers in a relatively short time at roomtemperatures, it is preferred to add a catalyst such as an organiccompound or mixture of compounds of certain polyvalent metals, forexample, those of tin, bismuth, antimony, lead and mercury. Examples aredibutyltin dilaurate, bismuth octoate, antimony octoate, lead octoate,lead naphthenate, mercuric acetate, phenyl mercuric hydroxide, phenylmercuric acetate, etc.

it will be understood that rather than providing a paste containing NCOterminated material, two-part sealant systems can be used in which onepart contains a diisocyanate prereacted with a portion of the hydrogencontaining material and the other part contains the balance of astoichiometric amount of hydrogen containing material sufficient toreact with all of the NCO groups in the system. in such cases the leadsalts of carboxylic acids and organo mercuric compounds, or combinationsthereof as catalysts are preferred since these tend to catalyze theNCOl-l reaction preferentially to the NCO water reaction to providequick boclying of the sealant. On the other hand, in the case of amoisture curable NCO terminated paste it is preferred to use a tin orother metallic salt suitable to catalyze the desired NCO water reaction.

The following reactions are believed to be involved: 1. The NCOterminated prepolymer is formed with a ratio of 2 NC() groups per activehydrogen by addition reaction an organic diisocyanate with an activehydrogen containing composition.

IIICO I NCO 2. A silane having a single reactive hydrogen is then added:

It is theorized that the siloxane is hydrolyzed on the surface to whichthe sealant is applied as follows:

and that further, a condensation next takes place with SiOH in the caseof glass to form a. permanent chemical bond as follows:

While the preferred curable materials of this invention are formed byreaction of a polyol and a polyisocyanate, it will be understood thatpolymeric isocyanates, such as polymethylene polyphenyl polyisocyanate(PAPl) having a similar molecular weight and functionality, can besubstituted. The isocyanate terminated curable material, prepolymer orotherwise, should have an average molecular weight between about 200 and20,000 and should have an average of about 2 to 8--NCO groups peraverage molecular weight.

The invention will be further understood with reference to the followingexamples. All parts are by weight unless otherwise specified. Allcompositions were cured at 75 F. and 50 percent relative humidity unlessotherwise specified. The adhesion tests employed were performed inaccordance with ASTM test method D903-49 Peel or Stripping Strength ofAdhesives." Immediately prior to running of the tests the substratesused in the test were cleaned with acetone until free from grease,moisture, and other impurities. The sealant specimens were cured on thecleaned substrates at 77 F. and 50 percent relative humidity until aconstant hardness indicated complete cure.

EXAMPLE I An OH terminated adduct wa's formed from the followingingredients:

Parts Polyoxypropylcne glycol (0H No. 38.7) 725.0 HexamethyleneDiisocyanutc 21.0

The ingredients were charged to the 1 liter resin reaction flask under 1cubic foot per hour dry N and heated with stirring to 100 C. After 4hours at that temperature, the product was cooled to 45 C. The resultantadduct had an hydroxyl number of approximately 18.8. (Hydroxyl number asherein used can be defined as the mg. of KOH equivalent to the OHcontent of 1 gram of the sample.) The adduct was reacted further to forman NCO terminated prepolymer:

Parts Adduct (OH No. 18.8) (equiv. wt. 2984) 298.4 PolyoxypropyleneTriol (0H No. 28.9) wt. 1940) 194.0 Toluene Diisocyunate (80% 2,4I20%2,6) 34.8

Dibutyltin Dilaurate 0.]

The first three of the ingredients listed were charged to a nitrogenswept 1 liter resin reaction flask and heated with stirring to 80 C.This temperature was maintained 4-hours. The prepolymer was then cooledto 60 C. and the catalyst, dibutyltin dilaurate, added. This prepolymerhad an NCO equivalent weight of approximately 2,600 and was a clear,colorless liquid with a viscosity of approximately 100 strokes.

The prepolymer was then further processed to form a sealant:

Parts Prepolymer 100.0 Rutile TiO dry l 3.9 Zinc Oxide, dry 13.9Magnesium Silicate, dry, finely divided 33.4

Methylaminopropyltrimethoxysilane I .4

EXAMPLE II Parts Polyoxypropylene glycol (OH No. 36.2) 700.0Polyoxypropylene triol (OH No. 29.7) 850.0 Toluene diisoeyanate (80/20ratio of 2,4- to 2,6-isomers) 156.6 Dibutyltin dilaurate L The firstthree ingredients were charged to the 2 liter resin reaction flask,heated to 80 C. under dry nitrogen with stirring. After 4 hours at thattemperature, product was cooled to 60 C., the dibutyltin dilaurateadded, cooled to 50 C. The resulting prepolymer was then furtherprocessed to form a sealant.

Parts Prepolymer 500.0 Finely divided dry silica flour 25.0 Carbon black(dry) 40.0 ZnO (dry) 25.0 Rutile TiO, (dry) 25.0 Magnesium silicate(dry) 370.0 2(2-hydroxy 5' methylphenyhbenzotriazole 5.0Methylaminopropyltrimethoxysilane 7.0

All ingredients excepting the silane were mixed under dry nitrogen for 1hour. The methylaminopropyltrimethoxysilane was then added and mixed 5minutes. The resultant sealant, a thixotropic paste, cured when exposedto moisture in the atmosphere to a rubber with tensile strength ofapproximately 200 p.s.i. and ultimate elongation of 200 percent, Shore Ahardness of approximately 55. As the compound cured, it developedexcellent adhesion to unprimed glass. The cured compound on unprimed oruntreated glass yielded a 180 peel value of pounds per inch width at apeel rate of 2 inches per minute with 100 percent cohesive failure ofthe sealant or adhesive. This adhesion was retained even after long termimmersion under water for a period of several months.

The example was repeated substituting a difunctional amino silane, gammaaminopropyltriethoxysilane, for the methylaminopropyltrimethoxysilane.The mixture gelled" or increased in viscosity on addition of the silane,indicating the occurrence of a chain extension reaction. The resultingcompound when fully cured had a tensile strength of 254 p.s.i., ultimateelongation of 200 percent and Shore A, hardness of 50. When cured onglass the sealant gave a 180 peel value of pounds per inch width at apeel rate of 2 inches per minute. After 4 days water immersion the peelvalue was only 4 pounds per inch width at the same peel rate, withadhesive failure of the sealant from the glass.

The example is repeated except that no silane was added. The resultingsealant when fully cured had a tensile strength of 337 p.s.i. andultimate elongation of 175 percent. When cured on glass the sealant gavea 180 peel strength of only 4 pounds per inch width at a peel rate of 2inches per minute, failing adhesively from the glass, without waterimmersion.

EXAMPLE Ill The prepolymer of example ll was mixed with the followingingredients:

Parts Prepolymer $00.0 Finely divided dry silica flour 25.0 Carbon black(dry) 40.0 Zinc oxide (dry) 25.0 Rutile no, (dry) 25.0 Magnesiumsilicate (dry) 370.0 2(2'-hydroxy 5 methylphenyhbenzotriazole 5.0Mercaptoethyltrimethoxyailane 7.0

The ingredients were mixed and reacted under the same conditions as setforth in example 11. The resulting sealant displayed excellent adhesionto unprimed glass, had a tensile strength of 310 p.s.i. and ultimateelongation of 125 percent. After 8 days water immersion the 180' peelvalue on glass at a peel rate of 2'inches per minute was 17 pounds perinch width with cohesive failure of the sealant.

EXAMPLE IV The preparation of an N-substituted aminosilane adduct wasconducted as follows:

Ingredients Pans Arninopropyltrimethoxysilane 22.1 Acetic anhydride 6.27

The acetic anhydride was added dropwise with stirring over a 15-minuteperiod to the aminopropyltrimethoxysilane. An exothermic reaction wasnoted. The following reactions are believed to have occurred, resultingin the formation of a silane adduct having a single active hydrogenNH2(CH2);Sl(OCHa) (CHaCO)zO H CH3CNH(OH2):S1(OCH;); CHaCOOH CHaCOOHexcess NH2(CH2);S1(O CHz)a An isocyanate-terminated prepolymer wasprepared as follows:

lngredients-Prepolymer Parts Polypropylene glycol (OH No. 41.8) 643.3

Polyether triol (OH No. 27.0) 995.0

Toluene diisocyanate'(80/20 ratio of 2,4

2,6-isomers) 166.6 Dibutyl tin dilaurate 1.5

The first three ingredients were charged to a reaction vessel and heatedto 80 C. under dry nitrogen with stirring. After 4 hours at thattemperature, the product was cooled to C.; the dibutyltin dilaurateadded, and the mixture was cooled to 50 C. The resulting prepolymer,together with the above silane adduct was then further processed'to forma sealant as follows:

Ingredients-Finished Sealant Parts Prepolymer 500 Finely divided drysilica 15 Carbon black (dry) 40 ZnO (dry) 25 RutileTiO (dry) 25Magnesium silicate (dry) 370 2(2'-hydroxy 5 methyl phenyl) benzotriazole5 Dibutyl tin dilaurate 1 Silane adduct 7 400 parts of the prepolymerand all of the other ingredients except the dibutyl tin dilaurate andsilane adduct were mixed together under dry nitrogen for 30 minutes toobtain a good dispersion. The remaining 100 parts of prepolymer werethen added and allowed to mix under dry nitrogen for 15 minutes. Thedibutyl tin dilaurate was then charged into the batch and mixingcontinued for an additional 45 minutes under dry nitrogen. The silaneadduct was added as a final step, and the batch was mixed for 15 minutesunder dry nitrogen. The resultant sealant, a thixotropic paste, curedwhen exposed to atmospheric moisture, to a tough, flexible, rubber. Asthe compound cured, it developed excellent adhesion to unprimed glass.When a one-eighth inch thick spread of this sea lant was allowed to curefor 7 days on unprimed glass at 75 F and 50 percent relatively humidityand the resultant bond immersed in water, it retained excellent adhesionto the glass even after 1 month immersion.

EXAMPLE V Substantially the procedure of example II was followed toprovide a prepolymer from the following ingredients:

The resultant sealant was obtained substantially as in example ll andhad the following composition:

Prepolymer (above) Pyrogenic silica (dry) Carbon black (dry) Rutiletitanium dioxide (dry) Magnesium silicate (dry) Zinc oxide (dry)2(2'-hydroxy 5' methylphenyl) benzo triazoleMethylaminopropyltrimethoxysilane This sealant was approximately 100percent end-blocked with methylamino-propyltrimethoxysilane. Itsproperties, after curing, were as follows:

Tensile strength 418 p.s.i. Elongation 25% Rex hardness 85 Glassadhesion Good EXAMPLE VI The procedures and formulations of example Vwere followed, except that 76.5 instead of 102 parts of the silane wereused, thus providing 75 percent end-blocking. The properties of thecured adhesive were:

Tensile strength 760 Elongation 35 Rex hardness 80 Glass adhesion GoodAlthough the properties of the adhesive of examples V and VI areadequate for many uses, the tear resistance of the cured polymer issubstantially less than that of cured adhesives made according to thisinvention with less silane end-blocking. This is particularly true inthe case of the 100 percent end-blocked embodiment of example V. Thatis, to improve the tear resistance, it is preferred that the amount ofend-blocking be less than lOO percent, e.g. 95 percent or less.

Whatl claim is:

l. A curable fluid organic material suitable for use as a sealant, saidmaterial having an average molecular weight between about 200 and about20,000, and having about 2 to about 8 functional groups per averagemolecular weight, selected from the group consisting of (a) N c 0 and(H) -NHCRi-R2-Sl( O R) a where V R is a lower alkyl group,

where R, is an alkyl, substituted alkyl, aryl, substituted aryl, or

where R is an alkyl, substituted alkyl, aryl, or substituted aryl group,

R is an alkylene group having two to 18 carbon atoms,

R, R R R and R being free of active hydrogens, at least 5 percent of thetotal of said (a) and (b) groups in said material being said group (b).

2. A material according to claim 1 wherein said curable fluid organicmaterial is prepared from a reaction mixture comprising:

an NCO terminated organic material having about 2 to about 8-NCO groupsper average molecular weight and a silane of the formula HR,--R Si(OR)wherein R, R and R, are as in claim 1 and H is an active hydrogen asdetermined by the Zerwitinoff Test,

said NCO terminated organic material having been prepared from areaction mixture comprising:

a compound containing at least two active hydrogen-bearing functionalgroups, as determined by the Zerwitinoff Test, and

an organic polyisocyanate, the ratio of equivalents of saidpolyisocyanate to said active hydrogen-bearing compound ranging from1.05:1 to 6:1.

3. A material according to claim 2 wherein the said ratio of equivalentsranges from 1.411 to 3:1.

4. A material according to claim 2 wherein said organic polyisocyanateis an aromatic diisocyanate and said active hydrogen-bearing compound isa polyalkyleneether glycol.

5. A material according to claim 2 wherein said silane is selected fromthe group consisting of an alkylaminoalkyltrialkoxysilane; amereaptoalkyltrialkoxysilane; and

wherein R and R are as defined in claim 2.

6. A material according to claim l wherein each R is a methyl group.

7. A sealant composition comprising a curable fluid organic materialaccording to claim 1.

8. A sealant composition according to claim 7 wherein said compositioncontains a finely divided filler in an amount sufficient to form athixotropic paste.

9. A sealant composition according to claim 8 wherein said fillercomprises finely divided silica.

10. A sealant composition according to claim 1 wherein about 50 percentor less of said (a) and (b) groups in said material are said group (b).

l l. A curable fluid -NCO--terminated polyurethane prepolymer suitablefor use as a sealant, said prepolymer having an average molecular weightbetween about 200 and about 20,000, said prepolymer being prepared by:

l. forming an -NCO terminated material having about 2 to about 8 NCOgroups per average molecular weight, by reacting a compound containingat least two active hydrogen atoms as described by the Zerwitinoff Testwith 1.4 to 6.0 equivalents, per equivalent of said compound. of anorganic polyisocyanate, and

2. thereafter reacting said material with a silane of the formulaHR,R,-Si(OR) wherein R, R and R, are as in claim 1, the proportions ofsaid silane being such that at least about percent of the -NCO groups ofsaid NCO terminated material are reacted with said silane.

12. A glass substrate coated with the material of claim 1.

13. A composition curable to a tough, flexible product, said compositioncomprising:

1 An NCO terminated prepolymer having about 2 to about 8 NCO groups peraverage molecular weight, said average molecular weight being betweenabout 200 and about 20,000, said prepolymer having been derived from areaction mixture comprising a compound having at least two activehydrogen-bearing groups, as determined by the Zerwitinofi test, andl.05-6.0 equivalents, per equivalent of said active hydrogen bearinggroup, of an organic polyisocyanate;

2 Up to about 50 percent by weight of filler, and

3 lnteracted with said prepolymer, at least about 0.7 weight percent andup to about L4 weight percent, based on the total of components (l)-(3),of a silane of the formula HR,-R Si(OR);,, where R is a lower alkylgroup,

where R;, is an alkyl, substituted alkyl, aryl, substituted aryl, or

where R is an alkyl, substituted alkyl, aryl, or substituted aryl group,R, is an alkylene group having two to 18 carbon atoms, R, R,, R R and Rbeing free of active hydrogens, and

H being an active hydrogen. 14. A glass substrate coated with thecomposition of claim 13.

15. A composition curable to a tough, flexible product, said compositioncomprising:

1 500-996 parts by weight of an NCO terminated prepolymer having about 2to about 8 --NCO groups per average molecular weight, said averagemolecular weight being between about 200 and about 20,000, saidprepolymer having. been derived from a reaction mixture comprising acompound having at least two active hydrogen-bearing groups, asdetermined by the Zerwitinofi test, and l.05-6.0 equivalents, perequivalent of said active hydrogen-bearing group, of an organicpolyisocyanate;

2 interacted therewith, 7-76.5 parts by weight of a silane of theformula HR,R,Si(OR),, where R is a lower alkyl group,

where R, is an alkyl, substituted alkyl, aryl, substituted aryl, or

17. A composition according to claim 15 wherein said compositioncontains up to 950 parts by weight of a filler.

* F I I P t nt No- 3,627,722 Dated December 1 1, 1971 Inventor) GeorgeM. Seiter It is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as ahownbelow:

Column 1, line 75 (last line), "HE in the formula should 7 be HR Column2, line 23, after the formula "HS(CH Si(OC H insert or at the end of theline and before the next formula.

Column line 71, in the second Table in Example I, after "(OH No. 28.9)"insert (equiv. so that the line will read Polyoxypropylene Triol (OH No.28.9)

(equiv. wt. 1940) 19 0 Column 6, line 58, second Table in Example IV,

"Dibutyl tin dilaurate" should be in small print and included as thelast line in the Table.

Column 7, line 15, "relatively" should be relative line &2, delete thehyphen in the word "methylamino-propyltrimethoxysilane".

Column 9, line 3 4 (in Claim 13), second formula, delete the second"or", which is repetitious.

Signed and sealed this 20th day of February 1973..

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents

2. A material according to claim 1 wherein said curable fluid organicmaterial is prepared from a reaction mixture comprising: an -NCOterminated organic material having about 2 to about 8-NCO groups peraverage molecular weight and a silane of the formula HR1-R2-Si(OR)3,wherein R, R1, and R2 are as in claim 1 and H is an active hydrogen asdetermined by the Zerwitinoff Test, said -NCO terminated organicmaterial having been prepared from a reaction mixture comprising: acompound containing at least two active hydrogen-bearing functionalgroups, as determined by the Zerwitinoff Test, and an organicpolyisocyanate, the ratio of equivalents of said polyisocyanate to saidactive hydrogen-bearing compound ranging from 1.05:1 to 6:1. 2.thereafter reacting said material with a silane of the formulaHR1-R2-Si(OR)3 wherein R, R1, and R2 are as in claim 1, the proportionsof said silane being such that at least about 5 percent of the -NCOgroups of said -NCO terminated material are reActed with said silane. 3.A material according to claim 2 wherein the said ratio of equivalentsranges from 1.4:1 to 3:1.
 4. A material according to claim 2 whereinsaid organic polyisocyanate is an aromatic diisocyanate and said activehydrogen-bearing compound is a polyalkyleneether glycol.
 5. A materialaccording to claim 2 wherein said silane is selected from the groupconsisting of an alkylaminoalkyltrialkoxysilane; amercaptoalkyltrialkoxysilane; and wherein R and R2 are as defined inclaim
 2. 6. A material according to claim 1 wherein each R is a methylgroup.
 7. A sealant composition comprising a curable fluid organicmaterial according to claim
 1. 8. A sealant composition according toclaim 7 wherein said composition contains a finely divided filler in anamount sufficient to form a thixotropic paste.
 9. A sealant compositionaccording to claim 8 wherein said filler comprises finely dividedsilica.
 10. A sealant composition according to claim 1 wherein about 50percent or less of said (a) and (b) groups in said material are saidgroup (b).
 11. A curable fluid -NCO-terminated polyurethane prepolymersuitable for use as a sealant, said prepolymer having an averagemolecular weight between about 200 and about 20,000, said prepolymerbeing prepared by:
 12. A glass substrate coated with the material ofclaim
 1. 13. A composition curable to a tough, flexible product, saidcomposition comprising: 1 An -NCO terminated prepolymer having about 2to about 8 -NCO groups per average molecular weight, said averagemolecular weight being between about 200 and about 20,000, saidprepolymer having been derived from a reaction mixture comprising acompound having at least two active hydrogen-bearing groups, asdetermined by the Zerwitinoff test, and 1.05-6.0 equivalents, perequivalent of said active hydrogen bearing group, of an organicpolyisocyanate; 2 Up to about 50 percent by weight of filler, and 3Interacted with said prepolymer, at least about 0.7 weight percent andup to about 1.4 weight percent, based on the total of components(1)-(3), of a silane of the formula HR1-R2-Si(OR)3, where R is a loweralkyl group, where R3 is an alkyl, substituted alkyl, aryl, substitutedaryl, or where R4 is an alkyl, substituted alkyl, aryl, or substitutedaryl group, R2 is an alkylene group having two to 18 carbon atoms, R,R1, R2, R3, and R4 being free of active hydrogens, and H being an activehydrogen.
 14. A glass substrate coated with the composition of claim 13.15. A composition curable to a tough, flexible product, said compositioncomprising: 1 500-996 parts by weight of an -NCO terminated prepolymerhaving about 2 to about 8 -NCO groups per average molecular weight, saidaverage molecular weight being between about 200 and about 20,000, saidprepolymer having been derived from a reaction mixture comprising acompound having at least two active hydrogen-bearing groups, asdetermined by the Zerwitinoff test, and 1.05-6.0 equivalents, perequivalent of said active hydrogen-bearing group, of an organicpolyisocyanate; 2 interacted therewith, 7-76.5 parts by weight of asilane of the formula HR1-R2-Si(OR)3, where R is a lower alkyl group,where R3 is an alkyl, substituted alkyl, aryl, substituted aryl, orwhere R4 is an alkyl, substituted alkyl, aryl, or substituted arylgroup, R2 is an alkylene group having two to 18 carbon atoms, R, R1, R2,R3, and R4 being free of active hydrogens, and H being an activehydrogen.
 16. A glass substrate coated with the composition of claim 15.17. A composition according to claim 15 wherein said compositioncontains up to 950 parts by weight of a filler.